Impact mills of this type are either employed for crushing tasks or only as impact dehullers to separate brittle shells, such as the shells of soybeans or cocoa beans and of other husk fruits, or, in general terms, to separate the seeds from the kernels. In DE-C 529 396 there is disclosed an impact mill comprising a vertical driving shaft with a throwing rotor as a distribution head attached thereto. Coaxially to the driving shaft, there is arranged a cylindrically-shaped, stationary body closed at its bottom side, comprising screen sections and in-between some beaters. The distribution head includes a disk with blades on its circumference, with the disk being attached to the driving shaft in an inclined arrangement. Raw material is supplied through a drum sieve until the body, or the drum sieve is almost filled. The filling ratio is held constant during operation. Due to the particular type of this construction and the operating mode, the raw material emitted by the lower blade is not capable of exerting any impact effect upon the beaters and the drum sieve as this blade solely digs through the raw material. Thus, an impact effect is only exerted by the upper blade. As a result, the drum wall will be subjected to an irregular wearing effect.
The U.S. Pat. No. 2 352 327 discloses mill, in which both a distribution head rotatable about a vertical rotational axis and a cylindrically-shaped impact ring arranged coaxially thereto are driven, with the distribution head and the impact ring being driven with different speeds. On its bottom side, the impact ring is supported by toothed wheels meshing with said impact ring. By designing this edge region in a wavelike way, an oscillating vertical motion of the impact ring will be accomplished for realizing a uniform wear of the annular lining exchangeably fastened to the impact ring by extending the surface of the impact ring hit by the particles, which in turn will result in a longer service life. The drawbacks of this construction are to be found, on the one hand, in its higher expenses for equipment, and, on the other hand, in the difficult guidance of the impact ring within the housing, since with this construction a tilting of the ring will be highly probable. In addition, the upper and lower dead points of the wave curves will lead to a longer biasing of the impact ring at those points, thus entailing an irregular wear of the annular coating.
It is an object of the present invention to avoid the drawbacks mentioned above and to suggest an impact mill, whose impact body is subjected to a uniform wear by constructionally simple means.